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William Lane Craig doesn’t understand Model-Dependent-Realism

October 2, 2012

In 2010, Stephen Hawking and Leonard Mlodinow released The Grand Design. This popular science book was written to educate about new fields of physics, such as quantum mechanics and quantum theory, and to promote the concept of M-theory. M-theory holds that there is no single unified theory for all physics, but rather that different physics theories are relevant in different contexts. So for an object the size of a  football, Newtonian physics will describe it’s behaviour. But if the football was shrunk to the size of an electron, quantum mechanics would better describe its behaviour.



So far, so uncontroversial.  Then Hawking and Mlodinow (shortened to Hawking)   take the next step by saying that because no one theory explains all observed  aspects of the universe, different models may be considered equally real if they provide equally accurate predictions that correspond with observed results.  They refer to this scientific approach as Model-Dependent Realism.


It was at this point that many philosophers simultaneously barfed on their tweed jackets.  One of the loudest barfers was Dr. William Lane Craig. Craig is a research professor of philosophy at the Talbot School of Theology, but is best known for debating prominent atheists. Craig has written a detailed post detailing his disagreements with Hawking, which has been taken up on many theist blogs as a ‘debunking’ of Hawking’s position. When I read Craig’s post, it struck me as poorly reasoned, but poorly reasoned in an instructive way. It seems to me that many of the flaws in contemporary philosophical-scientific communication were on full display in his post.


The main bulk of Craig’s argument is model-dependent realism is really a cover term for a philosophical position called ontological realism.  Now I imaging many of you might be asking “onty-whaty?”  It’s not exactly a household term. To make sure I was using the same definition as Craig, I looked the reference Craig alludes to in his post. Craig only mentions a “scholarly article in Blackwell’s Contemporary Debates on Metaphysics.” Google scholar led me to an article published called “The Picture of Reality as an Amorphous Lump” by Matti Eklund from the University of Colarado. This was published in 2008, so it’s a bit surprising that Craig would be reading it by chance four years late on the same morning as reading The Grand Design .  However,  it uses the same definition as Craig does, and also the same examples (e.g. do composite objects exist), so I think it’s safe to say it’s the same journal article. In it ontology is defined  the study of what there is (Huh? Doesn’t that make all scientific endeavour a form of ontology?) . Ontological pleuralism is the position that there is no “right” answer to ontological questions. For example, asking how many objects are inside a cage containing three bears, an ontological pluralist would argue that saying there are three single bears or one group of bears are both equally true. So an ontological pluralist might say that there is no single right way to describe reality, as any one way is no more or less correct than another

What Craig was conspicuously failing to put forward was a point-by-point list of similarities between the two theories, and (assuming he wanted to appear like a respectable academic) a list of their dissimilarities. These lists never eventuate. Instead, Craig apparently wants us to accept that model-dependent-realism and ontological pleuralism are the same thing because…well basically because he says so. Like he points out in his post, he spends his Monday mornings reading scholarly metaphysics papers, so who are we to ask for a positive argument linking the two?

Rather than taking the time to put forward an intellectual case, Craig instead devotes his wordspace to turning the scorn up to eleven. He portrays proponents of ontological pleuralism to be as radical and extreme as possible.  In his post, he describes ontological pleuralism as a “radical view defended by a handful of philosophers”, and Hawking’s position  as “even more radical than ontological pleuralism”, “more-anti-realist than positivist”  and Hawking and Moldinow as “extreme anti-realists”. I nearly wore out my dictionary keeping up with Craig’s reciting of philosophical positions, and found Hawking’s book on advanced physics a picture of crystalline clarity in comparison.


So just how alike are model-dependent-realism and ontological pleuralism?


Let’s compare the two. Model-dependent realism is a theory in physics that can be used to understand the limitations of certain theories, and evaluate which one is most appropriate for a certain context. For example, suppose I asked you how to get to the post office. You might reply that it is 500 metres down the  road. Is this real? Sure, in one sense it is. On the other hand the earth is moving at  108,000 kilometres per hour, so the post office won’t occupy the same point in space when you get to it as that which is “500 metres down the road” initially. So in that case, the description “500 metres down the road” does not reflect reality. If one wanted to be very accurate directions, one could calculate where in the solar system the post office would be when you reach it. However the Milky Way Galaxy is also moving, so even those co-ordinates won’t reflect the “real”  post office location. So the  “reality” of how to get to the post office is dictated by the model one uses to describe it.


Model-Dependent Realism is important in physics because each theory is only relevant to the point at which it accurately predicts what we observe in the world. This is manifestly not a position that nothing is real.  Rather it is a recognition that much of reality is beyond the reach of our senses, and that we can only recognise it by using scientific models. You and I have never seen a quark, but we understand quarks to be a part of reality because they are part of a model whose testable predictions have been borne out.  Yet models may only describe reality up to a point, then it fails and another theory takes over.  This happened when we discovered limits to Newtonian physics and adopted Einstein’s theory of relativity, and happened again when the limits of relativity were reached and quantum mechanics was adopted. This doesn’t mean any theory is “unreal”. It just recognises that however well a model explains the universe, there is always another layer to reality and hence our understanding of reality is incomplete, and is only as good as our scientific models are. this is emphatically not controversial in scientific circles.


Hawking uses this model-dependent realism to lead into his idea that M-theory is the only candidate for a complete theory of the universe.  M-theory is described as  a whole family of different theories, each of which is a good description of observations only in some range of physical situations. The analogy that Hawking uses is that of a flat map of the world, which can only be created by a collection of maps, each of which covers a limited area. In this sense the world map represents physics made up of a collection of connected physical theories, each which represents reality only within a specified reference frame.  This is the link between model-dependent-realism and a complete theory of the universe.


In contrast to the sweeping and thought-provoking claims of Hawking and Mlodinow, ontological pleuralism is a much duller enterprise altogether. Eklund’s  paper is not on whether there is an ultimate reality., as Craig claims. Rather it talks about whether ontological questions, e.g. do abstract objects exist?, are important questions  and on a par with scientific questions. He describes people who say ontological questions are not important as ontological pluralists, and attributes to them the view that a “cookie-cutter” view of reality, which means that all reality is one continuous entity, and labelling one part as different as others is like cutting a cookie out of amorphous dough, i.e. applying a human concept onto an indifferent universe.  An important point is that Eklund’s papier is concerned not with how reality is, but rather how we describe reality. As Eklund says “To this extent the disputants are simply speaking different languages…Whereas it might sound deep, there is nothing more deep than when you claim a tomato is a fruit and I claim it is a vegetable….the dispute is in an important sense verbal”.


Now we come to the big question…is Craig accurate when he says model-dependent realism and ontological pleuralism are the one and the same? Let’s break it down into components:

A) Model-dependent realism is used to explain how physics behaves differently at different scales of size. Ontological pleuralism is really talking about semantics, as in is any one word used to describe something more real than another appropriate word.

B) Model-dependent realism accounts for how it is meaningless to discuss the reality of a situation, not because there is no objective reality but because that much of objective reality (e.g. quarks, photons) is so counter-intuitive and alien to our sense of logic that it is only through mathematical models that we can appreciate them, yet our models will always have limits Ontological pleuralism says that the germane issue is what is the correct descriptive term to say in English.

B)  Model-dependent realism is used to explain scientifically measured data, for example why electrons move as a wave and why objects as large as you or I move like a particle. Ontological pleuralism cannot be sued to interpret any scientific data.

C) Model-dependent realism reinforces the idea that no matter how well we think we understand reality, there is likely to be a new theory developed later that will change how we understand the universe. In contrast ontological pleuralism only holds that some words are better for describing parts of the universe than others.

D) Model-dependent realism makes testable predictions, including that there are eleven dimensions of space-time, instead of the four (three of space and one of time) that we are accustomed to, and that seven of these are curled up into a very small, currently undetectable size. Ontological pleuralism makes no predictions, testable or otherwise.

E) Model-dependent realism takes no stand on wether incars, a type of car that only exists when it’s in a garage, is a real object or a figment of our imagination. To answer that questions you have to take two ounces of LSD and look in the phonebook for your local ontological pluralist.


To summarise, William Lane Craig likes to pass himself as a distinguished and wise academic, reluctantly forced to come down from his academic tower to correct the philosophical misunderstandings of atheists. This is an act. Craig is more like a second-hand car salesman as he will say whatever he thinks he can get away with to win an argument, regardless of wether it is true or not.




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  1. Very helpful. Thank you.

  2. Well done post. If you’re interested, I made a two-parts video where I argue how Craig misrepresented model-dependent realism. You can watch it at these links:, I’d be interested in your opinion.

  3. Thanks si. My apologies for the delay in putting your post up, as I just back from a long European trip. I’ll definitely check those youtube links out.


  4. greg lopes permalink

    Craig should consider the obvious advantages of becoming a model-dependent theist. A MD Theist could still plausible claim there is a reality distinct from models, just that we can never know that reality independently of our theories and models.

    As such Reality/God can only be partially understood as a condition of our models. Which it seems to me, is pretty much what rational, not dogmatic, theists and deists are arguing anyway.

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